Internal motor temperature has a critical effect on the performance and durability of electric motors. The internal temperature of an electric motor is greater than the ambient temperature due to the heat generated by the motor. In automotive engine cooling applications where the electric motor is under the hood of the vehicle the problem is made more severe by the high ambient temperatures produced by the vehicle's engine. Certain features may operate to reduce motor temperature rise over ambient temperature rise.
McLane-Goetz et al. U.S. Pat. No. 5,180,279 disclose a fan which includes a scoop downstream of an axial fan to divert some of the axial fan airflow across the rear of the motor.
DeFilippis U.S. Pat. No. 5,217,353 discloses a centrifugal blower motor having a stationary motor casing with holes for taking in air from the outside and for ventilating the interior of the motor; the motor also has a rotary part with holes which act as outlet ducts for the internal motor ventilation.
Ribs of the fan driven by the motor which are primarily structural can have the additional benefit of cooling the motor.